Reason Online features an interview with an outgoing SEC Commissioner. It makes sobering reading. Here's a taste:

reason: Why wouldn’t the market, this fierce disciplining force, create a system to certify trading activity and valuation?

Atkins: Well, there were outside parties—accountants, accounting firms, and, of course, the ratings agencies. Those were there to sort of give comfort to other parties, and the marketplace itself was starting to work on ways to try to have some sort of increased transparency with respect to these particular obligations. But the SEC has a statutory obligation to look at investment banks on a risk-management basis, to say, “What exactly do you think you’re worth, and how do you think you’re relating to the marketplace in general?” Those sorts of questions could have and probably should have been asked a little bit more forcefully.